Methods for photocuring liquid resin with reduced heat generation

Abstract

In a vat polymerization printer, a beam scanner scans a light beam across a mask and into a tank containing a photo-curable resin. The mask has pixels configurable to be individually transparent or opaque to portions of the light beam, which has a diameter greater than a cross-sectional dimension of the pixels of the mask. During an exposure time duration, a first subset of the pixels are controlled to be transparent at locations corresponding to the cross section of a three-dimensional object to be printed, while a second subset of the pixels are controlled to be opaque at locations not corresponding to the cross section of the three-dimensional object. The beam scanner is controlled to scan the light beam across the mask such that the light beam is always incident on at least one of the pixels of the mask that are controlled to be transparent.

What is claimed is: 
     
       1. A method for printing a cross section of a three-dimensional object in a photocuring region of a vat polymerization printer that includes (i) a tank configured for containing a photo-curable liquid resin, (ii) a flexible membrane defining a bottom boundary of the photocuring region, (iii) a light source configured to emit a light beam, (iv) a beam scanner configured to scan the light beam, and (v) a mask disposed between the beam scanner and the flexible membrane and having pixels configurable to be individually transparent or opaque to portions of the light beam, wherein a diameter of a cross section of the light beam is greater than a cross-sectional dimension of each of the respective pixels, the method comprising:
 controlling, during an exposure time duration, a first subset of the pixels to be transparent at locations corresponding to the cross section of the three-dimensional object, and a second subset of the pixels to be opaque at locations not corresponding to the cross section of the three-dimensional object; and 
 scanning, during the exposure time duration, the light beam across at least one region of the mask having at least some pixels that are controlled to be transparent and into the photocuring region, wherein at most ten percent of the pixels that are controlled to be opaque are scanned by the light beam during the printing of the cross section of the three-dimensional object, 
 wherein, during the exposure time duration, and as a result of the control of the first and second subset of the pixels, (i) a first region of the mask includes at least some pixels that are controlled to be transparent, the first region of the mask being surrounded by a first border with pixels that are controlled to be opaque, (ii) a second region of the mask includes only pixels that are controlled to be opaque, and (iii) a third region of the mask includes at least some pixels that are controlled to be transparent, and 
 wherein the scanning of the light beam comprises repeatedly scanning the light beam across the first region of the mask and into the photocuring region through pixels of the first region that are controlled to be transparent, repositioning the light beam from the first region of the mask to the third region of the mask without scanning the second region of the mask, and repeatedly scanning the light beam across the third region of the mask and into the photocuring region through pixels of the third region that are controlled to be transparent, 
 wherein the first border is illuminated by the light beam. 
 
     
     
       2. The method of  claim 1 , wherein repeatedly scanning the light beam across the first region of the mask comprises at least one of a raster scan or a back and forth scan of the first region of the mask, and wherein repeatedly scanning the light beam across the third region of the mask comprises at least one of a raster scan or a back and forth scan of the third region of the mask. 
     
     
       3. The method of  claim 1 , wherein, during the exposure time duration, a total number of pixels in the first subset of the pixels is less than a total number of pixels in the second subset of the pixels.